British officials rebuked President Donald Trump on Friday for claiming that the individuals responsible for setting off explosives in the London subway had been “in the sights of” law enforcement who failed to be “proactive.”

Prime Minister Theresa May reproached Trump for his rhetoric in the wake of what police are investigating as a terrorist attack that injured at least 29 people.

“I never think it’s helpful for anybody to speculate on what is an ongoing investigation,” she said. “As I’ve just said, the police and security services are working to discover the full circumstances of this cowardly attack and to identify all those responsible.”

Trump earlier on Friday had used the latest attack to offer tough talk on terrorism, and implied that Scotland Yard officials had fallen down on the job — although it’s unclear what non-public information, if any, the president based the comment on.

“Another attack in London by a loser terrorist,” Trump tweeted early Friday morning. “These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!”

He wrote in a follow-up post that “loser terrorists” should “be dealt with in a much tougher manner” and urged the U.S. to curb their internet access, which serves as a recruiting tool for terrorists.

“We must cut off & use better!” Trump said.

National security adviser H.R. McMaster appeared to try to clean up Trump’s comment, telling reporters later on Friday afternoon that Trump was speaking generally about Scotland Yard, and that he was trying to broadly convey that law enforcement is focused on the threat of terrorism.

“For years, Scotland Yard has been a leader, as our FBI has been a leader. So I think if there was a terrorist attack here, God forbid, that we would say that they were in the sights of the FBI,” McMaster said. “So I think he didn’t mean anything beyond that.”

Trump and his administration have stoked the ire of British officials before. The U.K. earlier this year temporarily ceased intelligence sharing with the U.S. after images from an attack in Manchester were leaked to and published in U.S. media, infuriating British officials. May had said she would “make clear to President Trump that intelligence that is shared between our law enforcement agencies must remain secure” when the two met at a NATO summit in May.

Speaking in Brussels that month, Trump condemned the “deeply troubling” leaks and said he would ask the Justice Department to review the matter and prosecute the culprit, if appropriate.

A White House official said on Friday that chief of staff John Kelly wasn’t with the president when he fired off his tweets about “loser terrorists” before 7 a.m. Kelly has tried to bring structure to the West Wing and contain some of the president’s impulses by serving as a gatekeeper to what people and what information make it into the Oval Office.

The official said it’s unclear whether Kelly has spoken with the president about his tweets, but Trump was scheduled to receive an intelligence briefing later Friday morning.

London Mayor Sadiq Khan, who clashed with Trump after an attack on the London Bridge area in June, said on Friday he been too busy working with police, security services and first responders to pay attention to Trump’s tweets.

“I haven’t had a chance to look at Twitter, let alone tweet,” he said.

A Metropolitan Police spokesperson dismissed Trump’s tweet in an interview with the Independent as “speculation.”

“We don’t even know who the suspects are so it’s a bit difficult to say,” the spokesperson said.

Nick Timothy, a former aide to May, echoed the prime minister’s sentiment. He said the tweet is “so unhelpful from leader of our ally and intelligence partner.”

Trump told reporters in the Rose Garden later Friday morning that the attack is “a terrible thing” and reiterated his calls for America to “be very smart” and get “very, very tough.”

“We’re not nearly tough enough,” said Trump, who added that he would call May on Friday. “That is just an absolutely terrible thing.”

May offered her thoughts to “those injured at Parsons Green and emergency services who are responding bravely to this terrorist incident” in her initial statement.

As of late Friday morning, Trump hadn’t publicly offered his thoughts and prayers or pledged America’s support to London, but the White House said he did so privately in a call with May.

Trump conveyed “his sympathies and prayers for those injured in the terrorist attack today in London,” the administration said in a statement. “The president pledged to continue close collaboration with the United Kingdom to stop attacks worldwide targeting innocent civilians and to combat extremism.”

Trump later said during a speech at Joint Base Andrews that he expressed “America’s deepest sympathy as well as our absolute commitment to eradicating the terrorists from our planet” to the British prime minister during the call. The president then vowed to eradicate “radical Islamic terrorism.” The Islamic State claimed responsibility for the attacks just prior to Trump’s appearance.

Trump also touted that the U.S. military’s capability could be “both effective and overwhelming” in responding to the threat of terrorism and that of North Korea, which Thursday launched yet another ballistic missile over Japan, inflaming tensions in the region.

Trump and May also spoke of the recent North Korean nuclear test, according to a U.K. readout of the conversation, “agreeing it was a reckless provocation and that China must now use all its leverage to bring pressure to bear on the North Korean regime to ensure they change course and end these illegal tests.”

Earlier on Friday Trump had followed up his tweets on the London incident with one criticizing the administration of former President Barack Obama while claiming success against fighting terrorists.

“We have made more progress in the last nine months against ISIS than the Obama Administration has made in 8 years,” he said in the tweet. “Must be proactive & nasty!”